A memory device may be disconnected or “powered-down” during a write/read operation. Such a loss in power may cause the write/read operation to terminate early, before completion. Early termination of the operation may cause data to be partially written/read, adding a significant amount of noise (or distortion) to the data, which may render the data unusable.
Multi-level cell memory devices may store multiple bits of data in each cell using multiple levels or pages of the memory. When a multi-level cell memory device powers-down during a write/read operation to one of the pages for a cell, noise may be added, not only to the data written to that page, but also to all previously programmed pages for that cell.
In order to avoid corrupting previously programmed pages, some systems generate backup pages for each page before programming the next level page in the multi-level cell memory device. In one example, a backup page may be generated for a most significant bit (MSB) page before programming the next sequential center significant bit (CSB) page and a backup page may be generated in turn for the CSB page before programming the next sequential least significant bit (LSB) page. In general, for an N-bits per cell memory device, to program the Nth bit level page, all prior N−1 pages may be backed-up.
Creating backups of all previously programmed pages to correct subsequently corrupted pages adds storage management and programming overhead that may reduce the device effective endurance, may be time consuming and may significantly degrade system performance.